The invention is related generally to improvements in broadcast transmitting antennas and more particularly to a novel type of stacker approach for accommodating two or more antennas on the same tower structure without the desired directional characteristics of the antennas being significantly degraded by scattering effects.
Broadcast transmitting antennas are usually array type antennas. The onset of DTV (digital television) has brought the need for additional tower space. For omni-directional coverage, the only solution usually is a top-mount antenna since omnidirectional antennas at other locations will exhibit azimuth patterns which are degraded by the scattering effects of other elements of the tower structure. Normally only one top-mount antenna can be considered per tower, since other antennas at the top of the tower will cause such scattering effects.
With this in mind, there is a need to have more than one omni-directional coverage antenna per tower. Currently, the only solution was to use an offset stack or stack two antennas and run the feeder for the upper antenna through the lower antenna aperture (xe2x80x9ccenterfed stackxe2x80x9d). Both of these solutions are accepted, but can cause undesired azimuth coverage patterns, i.e., significantly different from the desired omnidirectional pattern.
A general object of this invention is to provide improved azimuth coverage by incorporating the antenna design into the support structure.
In accordance with the invention, an antenna and tower structure mountable to a tower top or building top, comprises an elongated tower having a generally polygonal cross-sectional configuration and constructed having at least three spaced apart upright members defining said polygonal cross-sectional configuration and a plurality of cross members interconnecting said upright members, and at least one of said upright members of said elongated tower comprising an elongated antenna.